1. Technical Field
The present invention relates to an electronic component, a mounted structure, an electro-optical device, and an electronic device.
2. Related Art
Conventionally, technologies for packaging an electronic component, such as a semiconductor integrated circuit (IC), have been used in circuit boards or liquid crystal displays to be mounted on various electronic devices. For example, an IC chip for driving a liquid crystal panel is mounted on a liquid crystal display. The IC chip may be mounted directly on a glass substrate constituting the liquid crystal panel, or may be mounted on a flexible printed circuit (FPC) to be mounted in the liquid crystal panel. The mounted structure of the former is designated as a chip-on-glass (COG) structure, and that of the latter is designated as a chip-on-FPC (COF) structure.
As shown in FIG. 9(a), in a mounting process of the IC chip for driving the liquid crystal in the COG liquid crystal display, an IC chip 21 is placed on anisotropic conductive film (ACF) 222, which contains electrically conductive particles 222a dispersed in a thermosetting resin 222b, on a glass substrate 11. Upon heating and pressing of the IC chip 21 and the glass substrate 11, bump electrodes 21B and 21B on the IC chip 21 come into electrical contact with the arrays of electrode terminals 11bx and 11dx with the electrically conductive particles 222a therebetween. Then, the thermosetting resin 222b is cured to maintain the electrically conductive contact.
Typically, to ensure a highly reliable electrical connection between the metallic bump electrodes 21B and the electrode terminals 11bx and 11dx, the relative position between the IC chip 21 and the glass substrate 11 must be fixed while the electrically conductive particles 222a between them are elastically deformed. Thus, the electrically conductive contact through the electrically conductive particles 222a is maintained even when the thermosetting resin 222b thermally expands with temperature variations.
However, since the electrically conductive particles 222a are very small, it is very difficult to achieve the predetermined elastic deformation.
To solve this problem, as shown in FIG. 9(b), an invention in which a bump electrode 10 is composed of a resin bump 12 on an active surface of the IC chip 21 and an electrically conductive film 20 on the resin bump 12 has been proposed (see, for example, Japanese Unexamined Patent Application Publication No. 2-272737). Furthermore, an insulating film 26 is preformed on a pad 24 on the IC chip 21, and a part of the insulating film 26 is bored to form a connector 22 on the pad 24. Then, the electrically conductive film 20 of the bump electrode 10 extends to the connector 22, and thereby the bump electrode 10 can function as an electrode terminal of the IC chip 21.
When this bump electrode 10 is pressed against the terminal on the glass substrate, the resin bump 12 of the bump electrode 10 deforms elastically. Since the resin bump 12 of the bump electrode 10 is much larger than the electrically conductive particles in the ACF, a predetermined elastic deformation can be achieved. Under such a condition, after the IC chip 21 is fixed on the glass substrate using a thermosetting resin, the electrically conductive contact through the bump electrode 10 can be maintained even when the thermosetting resin thermally expands with temperature variations.
However, when the electrically conductive metallic film 20 is formed on the resin bump 12, the adhesion of the electrically conductive metallic film 20 is poorer than the adhesion of the electrically conductive metallic film on a metallic member. If the electrically conductive metallic film 20 detaches from the resin bump 12, the electrical connection between the bump electrode 10 and the electrode terminal on the glass substrate may be broken.
Furthermore, since the connector 22 is an opening in the insulating film 26 on the pad 24, a residual insulating film on the connector 22 may break the electrical connection between the bump electrode 10 and the pad 24.
Thus, under these defective conditions, the IC chip 21 may be electrically disconnected from the glass substrate. Accordingly, it would be desirable to increase the reliability of the electrical connection by improving the redundancy of the connection between the IC chip and the glass substrate.
The present invention was accomplished to solve the above-mentioned problems. It is an object of the present invention to provide an electronic component with excellent redundancy and a structure including the electronic component.
It is another object of the present invention to provide an electro-optical device and an electronic device both having a highly reliable electrical connection.